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<br />passageway is designed to withstand expected high flows during heavy runoff years. Figure 1 <br />presents an artist rendition of the fish passage while Figure 2 presents additional details. <br /> <br />A physical model of the dam with the proposed passage improvements was developed and tested <br />at Reclamation's laboratory in Denver, Colorado. Through a series of tests and modifications <br />under streamflows between 740 and 10,000 cfs, optimal placement and configuration of the rocks <br />was detennined. The pools would provide resting areas for migrating fish and the riffles would be <br />designed to accommodate the swimming speeds of the fish, <br /> <br />During low streamflows, a discharge of about 100 cfs would be needed to provide about 2 feet of <br />depth and a water velocity of about 3 feet per second through the notch in the diversion dam. <br />The results of the model testing indicated maximum water velocities in the riffle sections would <br />be between 3.5 and 4 feet per second under low water conditions. The pool and riffle design <br />would also maintain relatively low velocities at higher flows, <br /> <br />Under high streamflow conditions at certain times of the year, nonnative fish species can also <br />negotiate the present GVIC Diversion Dam without any improvements to the diversion dam. <br />Therefore, a fish trap to separate native and nonnative fishes would not be installed at this <br />structure. A strong population of nonnative fish already has become established upstream. In the <br />future, if a passageway is constructed at the Price-Stubb Darn, a fish trap for separation of native <br />and nonnative fishes may be installed at that location to prevent further upstream access by <br />nonnative fish. The Fish and Wildlife Service and Colorado Division of Wildlife are also <br />implementing a program to reduce the number of non-native fish in gravel pits and ponds along <br />the Colorado River that periodically flood and introduce the non-natives to the river environment. <br /> <br />Construction <br /> <br />Agreements such as easements would be required from private landowners and from GVIC prior <br />to construction, Protective measures would be negotiated with the private landowners to reduce <br />impacts during construction and to restore any damaged lands following construction, An <br />existing bridge to the site would be improved to more safely accommodate construction <br />equipment and the hauling of materials, Construction material may be stored on nearby vacant <br />land and the rocks would be obtained from existing commercial sources. A cofferdam would be <br />required to dewater the area where the riffles and pools would be constructed, A Section 404 <br />pennit, required under the Clean Water Act prior to any construction, has been applied for; and if <br />discharging water from dewatering is needed, a Section 402 pennit would also be obtained, <br />Construction. is scheduled for late 1997 or early 1998 during low water conditions and would be <br />done by GVIC work crews or a private contractor. Construction costs are between $250,000 <br />and $1,000,000 (an exact estimate has been developed, but is not presented in the EA due to <br />bidding processes) . <br /> <br />8 <br />